1. Field of the Invention
The invention relates to voice coil motors, and more particularly to driving circuits for voice coil motors.
2. Description of the Related Art
A voice coil motor is a linear DC motor and comprises a permanent magnet and a coil surrounding the permanent magnet. Generally, radio receiver loudspeakers have voice coil motors therein. Presently, voice coil motors are applied as actuators for servo control. For example, a voice coil motor is used as a driving motor for moving a pickup head of an optical disk drive. A voice coil motor generates a force in proportion to a current flowing through the coil of the voice coil motor. The voice coil motor therefore requires a driving circuit to generate a precise driving current to drive the voice coil motor to generate a precise moving force.
When a driving circuit generates a driving current to drive a voice coil motor, the driving current may jitter. Jittering of the driving current generates imprecise driving forces and lowers performance of voice coil motors. To prevent the driving signal of the voice coil motor from jittering, a conventional driving circuit usually comprises a complex component circuit to reduce jittering thereof. However, the component circuit comprises a plurality of diodes and a plurality of rectifying semiconductor elements, which increases manufacturing costs of the driving circuit. In another embodiment, a microcontroller or a digital signal processor is used to reduce uttering of the driving signal. The microcontroller or the digital signal processor, however, also increases manufacturing costs of the driving circuit. Thus, a driving circuit, manufactured at a low cost, with reduced jitter to drive a voice coil motor is called for.